Liquid sample pipette with detachable ejector

ABSTRACT

The sampling pipette comprises a body ( 2 ) and an arm movable relative to the body to eject a cone ( 9 ) fixed to the pipette, ejection taking place in a longitudinal direction ( 10 ) of the pipette, the arm having both a first portion ( 16, 18, 20 ) suitable for coming into contact with the cone, and a second portion ( 14 ). The two portions are engaged one in the other and, starting from an operating position, they enable the first portion to be separated from the body ( 2 ) by means of an initial movement in a direction that is essentially perpendicular to the longitudinal direction ( 10 ).

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/240,348 filed Mar. 24, 2003, which claims priority to InternationalApplication PCT/FR01/01071, filed Apr. 9, 2001, which claims priority toFrench Patent Application 00/04470, filed Apr. 07, 2000. Each of thesepriority documents, including the specification, drawings, claims, andabstract, are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to pipettes for taking liquid samples.

BACKGROUND OF THE INVENTION

A sampling pipette is known, e.g. from document FR 2,696,110, that issuitable for receiving a discardable cone at its bottom end, which coneis held on the pipette by means of friction. The pipette has an ejectorthat can be actuated by means of a button adjacent to a sampling button.Pressing on that button enables the cone to be pushed away from thepipette when it is desired to replace a used cone with a new cone.

In that pipette, the ejector has an arm with a bottom portion for cominginto direct contact with the cone, and a top portion to which the bottomportion is secured by friction engagement in the longitudinal directionof the pipette. This engagement enables the bottom portion of theejector to be assembled simply and quickly onto the pipette and to beremoved with the same advantages. Nevertheless, while ejecting a cone,at the moment when the cone gives way and becomes detached from the tipof the pipette, the ejector follows the cone and its speed increasessuddenly. The movement of the ejector is then stopped sharply becausethe top portion comes into abutment against the body of the pipette. Thesame braking force is transmitted to the bottom portion via the frictionengagement. Unfortunately, this force tends to undo the engagementbetween the bottom and top portions and to separate them from eachother. After ejecting some number of cones, it can thus happen that thebottom portion of the ejector becomes separated from the pipette inuntimely manner.

Document WO 96/37302

has a FIG. 19 providing for an ejector in which the bottom portion thatpushes against the cone is itself engaged in the longitudinal directionof the pipette in a top portion of the ejector. A fixing tongue holdstogether the two interconnected portions and prevents them fromseparating in untimely manner. Nevertheless, in order to remove thebottom portion, it is necessary to reach the tongue, and that is ratherawkward.

An object of the invention is to provide a pipette of a different typethat avoids untimely separation of the bottom portion of the ejector,but in which the ejector remains easy to remove.

SUMMARY OF THE INVENTION

To achieve this object, the invention provides a sampling pipettecomprising a body and an arm movable relative to the body to eject acone fixed to the pipette, ejection taking place in a longitudinaldirection of the pipette, the arm having both a first portion suitablefor coming into contact with the cone, and a second portion, wherein thetwo portions are engaged one in the other and, starting from anoperating position, they enable the first portion to be separated fromthe body by means of an initial movement in a direction that isessentially perpendicular to the longitudinal direction.

Thus, because the arm still comprises two portions that are assembledtogether, it can continue to be removed in simple manner. Nevertheless,the invention prevents the portions separating in untimely manner underthe effect of forces that arise during ejection. In addition, since thefriction connection is no longer essential, a connection can be providedthat is suitable for being assembled and disassembled without applyingforce.

The invention may also present at least any one of the followingcharacteristics:

-   -   the pipette is organized in such a manner that the engagement        direction is lateral;    -   the pipette is organized in such a manner that there is only one        engagement direction;    -   one of the arm portions is T-shaped, suitable for being received        in a correspondingly-shaped housing of the other portion;    -   the pipette is organized in such a manner that the two portions        can be separated from each other without previously        disassembling the pipette;    -   the body of the pipette forms an obstacle to separating the two        portions, at least when the arm lies at a high end of the        ejection stroke;    -   the pipette is organized in such a manner that the body enables        the two portions to be separated when the arm lies at a low end        of the ejection stroke; and    -   the pipette includes adjustment means, enabling the length of        the arm to be varied continuously over a range of values.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention appear furtherfrom the following description of a preferred embodiment given by way ofnon-limiting example. In the accompanying drawings:

FIG. 1 is a perspective view of the ejector mechanism of a pipetteconstituting a preferred embodiment of the invention;

FIG. 2 is a fragmentary axial section view of the pipette showing thelocation of the FIG. 1 mechanism;

FIGS. 3 and 4 are two perspective views of the actuator of the FIG. 1device;

FIG. 5 is a fragmentary axial section view on plane V-V of the FIG. 3actuator;

FIG. 5A is an axial section view on plane A-A of the FIG. 5 actuator;

FIGS. 6 and 7 are a rear view and a left-hand view of the connectionscrew of the FIG. 1 mechanism;

FIGS. 8 and 9 are two cross-section views on planes VIII-VIII and IX-IXof the FIG. 7 screw;

FIGS. 10 and 11 are a perspective view and an axial section view of theejector rod of the FIG. 1 mechanism;

FIG. 12 is a plan view of the FIG. 10 ejector 5 rod; and

FIG. 13 is a diagram showing how the ejector rod is put into place onthe pipette.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The sampling pipette constituting the present invention of the inventionis of the same type as that described in document FR-2,696,110.Reference should therefore be made to that document for various detailsof the pipette already disclosed therein. Only certain aspects of thecone ejector mechanism are described in detail below.

With reference to FIG. 2, the pipette conventionally comprises a body 2serving as a handle for holding in the user's hand. The pipette has apiston 6 that is slidably movable along a longitudinal axis 10 of thepipette in a bottom cavity of the pipette in order to suck up a volumeof liquid that is to be taken into said cavity, or else to expel ittherefrom. Displacement of the piston is controlled in particular bymeans of a control rod on the axis 10 having its bottom portionconnected to the piston by parts of known type. At its top end, the rodis surmounted by a pushbutton that is rigidly fixed to the rod and thatthe user can actuate with the thumb of the hand holding the pipette. Thepiston thus moves down and up as a function of the same movement of thebutton. The pipette includes a return spring suitable for returning thepiston and the rod to the high position at the end of their down strokefor expelling liquid, and a purge spring whose effect is added to thatof the preceding spring when the stroke of the piston is continueddownwards for a purge stroke. The pipette has a bottom tip 7 suitablefor receiving a discardable sampling cone 9 in conventional manner,which cone is held by friction acting on the outside of the bottom tip.

The pipette has a cone ejector mechanism as shown in FIGS. 1 and 2. Thismechanism comprises, going downwards along the longitudinal direction ofthe pipette: a control button 12; an actuator 14; a connection screw 16;a knurled wheel 18; and an ejector rod 20. The FIG. 1 ejector mechanismextends over the rear portion of the pipette, i.e. the portion besidethe palm of the user's hand.

The actuator 14 is generally elongate in shape in a downward directionand it tapers downwards. It is received in the body 2 of the pipette soas to be slidably movable therein along the axis 10. The pipette isarranged in such a manner that downward pressure on the button 12 causesthe actuator 14 to move down. The connection between the button and theactuator can be of conventional type and is not described herein. Areturn spring 19 shown in FIG. 2 serves to raise the actuator 14 whenforce is no longer applied to the button 12.

With reference to FIGS. 3, 4, 5, and 5A, the actuator 14 presents abottom end formed by a female coupling portion 22. This portion isshaped in a direction parallel to the axis 10 and has a generallyU-shaped cross-section, and more precisely a cross-section in the formof a portion of an ellipse with both limbs 24 of the U-shape extendingtowards each other at both ends. The opening 26 of the U-shape facessideways, in this case towards the left-hand side of the pipette. Thebottom edge of the coupling portion 22 has a shoulder forming a step 28projecting radially towards the inside of the U-shape. Nevertheless,this shoulder is also U-shaped. Each limb 24 is separated from theremainder of the actuator by a horizontal notch 30 extending from apoint situated about halfway along the length of the branch to the freeend thereof. The coupling portion forms a cavity 32 between the limbs24.

With reference to FIGS. 6 to 9, the connection screw 16 has a top head34. The head 34 includes a support 36 generally in the form of arectangular parallelepiped and a male coupling portion 38 suitable forpenetrating into the female coupling portion 22 of the actuator. Forthis purpose, the male coupling portion 38 is of constant sectionparallel to the axis 10, while transversely to said axis it is generallyof elliptical shape. The connection screw 16 has a core 40 from whichthe support 36 projects upwards, being offset laterally relativethereto. The height of the male portion 38 is less than the height ofthe support 36. The top ends of the male portion 38 and of the support36 are at the same level, but the male portion lies at a distance fromthe core 40 so as to enable the step 28 to pass between them. The maleportion 38 extends towards the right, projecting from the support 36,and also towards the front and towards the rear. Seen from the left andfrom the right it presents a T-shaped profile.

The male portion 38 is suitable for being received by being engaged inthe female portion 22 in a lateral direction perpendicular to the axis10. During insertion, the limbs 24 spread apart and then move backtowards each other, thereby producing a click indicating that the maleportion has reached its reception position. The limbs are capable ofbending because of the notches 30 and because of the material used,which in this case is a thermoplastic material. The step 28 takes upposition between the male portion 38 and the core 40. The connectionscrew 16 is thus rigidly assembled to the actuator 14. This assembly canbe disassembled. Assembly and disassembly are performed by moving thescrew in translation relative to the actuator in a left-right lateraldirection.

The core 40 of the connection screw has a flat top plate 42 and a thinbottom portion 44 of essentially rectangular section. At its bottom endit is extended by a threaded rod 46.

With reference to FIGS. 10 to 12, the ejector rod 20 is elongate inshape in the vertical direction. Its transverse section is essentiallyhollow and open. Nevertheless, this section is closed at the bottom end48 of the rod in order to form a ring that is engaged slidably on abottom endpiece 50 of the body 2 forming its bottom end 7, as shown inFIG. 2. The ring is suitable for coming directly into contact with thecone in order to eject it. In addition, the rod 20 is essentiallynon-rectilinear in shape so as to unite said bottom end 48 lying on theaxis 10 of the pipette with the rear portion of the pipette at the topend of the rod which is off-center relative to the axis 10.

At its top end, the rod presents a top vertical duct 52 of rectangularcross section extending from a top face 54 of the rod to a notch 56 cuthorizontally into the rod from its rear face and going towards its frontface. Beneath the notch, the rod has a bottom duct 58 coaxial with thetop duct 52, but this time of circular cross section. The diameter ofthe bottom duct 58 is equal to the width of the profile of the top duct52, and likewise the diameter of the threaded rod 46 of the screw 16 isequal to the width of the bottom portion 44 of the support.

The knurled wheel 18 has a central threaded duct to form a screw-and-nutconnection with the rod 46 of the screw 16.

The wheel 18 is received in the notch 56 in alignment with the ducts 52and 58. The screw 16 penetrates into both ducts and also into the wheel.The male portion 38 projects from the top face 54, with the rectangularportion 44 of the support being received in the top duct 52, therebypreventing the rod 20 from turning relative to the screw while allowingthem to slide relative to each other. The wheel 18 forms a screw-and-nutconnection with the rod 46 of the screw. The bottom portion of the screwis slidably received in the bottom duct 58. The rod 20 is thus connectedto the pipette firstly by the connection screw 16 and secondly by thering 48 engaged on the endpiece.

The wheel 18 is directly accessible to the user from behind the pipettethrough the notch. Turning the wheel causes the rod 20 to slide up ordown relative to the body 2 parallel to the axis 10, thereby adjustingits position as a function of the type of discardable cone used.

In order to eject a cone, the button 12 is lowered so as to bring therod 20 to the bottom end of its stroke, thereby pushing the conedownwards and detaching it from the pipette.

When the ejector mechanism is at rest, i.e. at the top end of itsstroke, the male and females portions 38 and 22 are received inside thebody of the pipette and they are inaccessible to the user. In addition,they are protected therein against impacts and against dirt. The rod 20cannot be removed while in this position.

In order to remove the rod 20 and separate it from the pipette, thebutton 12 is lowered so as to place the rod in its bottom end of strokeposition. The male and female portions are then visible. The rod 20 isthen pushed sideways to separate the male and female portions asdescribed above and as shown in FIG. 13. This causes the rod 20 to tiltrelative to the body of the pipette, with such tilting being possiblebecause of clearance at the ring 48. The bottom portion of the rod isthen slid downwards so as to disengage it from the pipette. Reassemblyis performed by following the same operations in reverse order. The rod20 can be assembled and removed without applying force, unlike thelongitudinal connection obtained by friction in the prior art.

It can thus be seen that the rod 20, the knurled wheel 18, and the screw16 constitute a first portion of the ejector arm suitable for beingengaged laterally in the second portion of the arm as formed by theactuator.

It should be observed that the rod can also be removed under suchcircumstances by turning the wheel until it becomes disengaged from theconnection screw 16. However that would separate the rod 20, the screw16, and the knurled wheel 18 from one another, whereas the proceduredescribed above keeps these three parts connected together.

Because of the step 28, the rod 20 cannot be separated from the actuator14 by sliding parallel to the axis 10. It is necessary to begin byimparting relative movement in a lateral direction. There is thus nolikelihood of untimely separation occurring while ejecting a cone.

The knurled wheel 18 serves to adjust the length of the ejector armconstituted by the actuator 14 and the rod 20 over a known range oflength values.

Naturally, numerous modifications could be applied to the inventionwithout going beyond the ambit thereof.

For example, the rod 20 could be connected to the actuator 14 byconnections of other types that impede relative sliding between theseparts of the ejector, for example one or more screw-and-nut connectionsor a bayonet type connection.

The characteristics enabling the length of the arm to be adjusted over aknown range of values can be implemented independently of thecharacteristics relating to the arm being made up of two portions thatare engaged one in the other and that can be separated in a directionthat is perpendicular to the longitudinal direction.

1. A sampling pipette comprising: (a) a body; and (b) an ejector arm attached to the body, the ejector arm comprising an ejector rod and an actuator connected to the ejector rod, wherein the ejector rod and the actuator are engaged one in the other such that the ejector rod and the actuator may be separated by moving the ejector rod sideways with respect to the actuator.
 2. The sampling pipette of claim 1, wherein the ejector rod can be separated from the actuator without removing the actuator from the body.
 3. The sampling pipette of claim 2, wherein the ejector rod can be separated from the actuator only when the ejector rod is at the bottom end of a purge stroke.
 4. The sampling pipette of claim 1, wherein the ejector rod and the actuator can be assembled in only one direction.
 5. The sampling pipette of claim 1, wherein the connection between the actuator and the ejector rod comprises a connection screw.
 6. The sampling pipette of claim 5, wherein the ejector rod comprises a vertical duct for housing the connection screw.
 7. The sampling pipette of claim 6, wherein the ejector rod further comprises a ring capable of slidable engagement with an endpiece of the body.
 8. The sampling pipette of claim 1, wherein the connection between the ejector rod and the actuator comprises a male-female connection.
 9. The sampling pipette of claim 1, wherein the connection between the ejector rod and the actuator comprises a bayonet-type connection.
 10. A sampling pipette comprising: (a) a body; (b) an ejector arm attached to the body, the ejector arm comprising an ejector rod and an actuator engaged one in the other through a connection, wherein the connection comprises a sideways facing generally U-shaped portion and a male portion adapted to be received in a lateral direction by the generally U-shaped portion.
 11. The sampling pipette of claim 10, wherein the generally U-shaped portion comprises a bottom edge comprising shoulder forming a step projecting radially from the inside of the U-shape.
 12. The sampling pipette of claim 10, wherein the male portion is disposed on a T-shaped connection screw.
 13. The sampling pipette of claim 12, wherein a support connects the T-shaped connection screw and the male portion.
 14. The sampling pipette of claim 13, wherein the T-shaped connection screw comprises a core and a threaded rod.
 15. The sampling pipette of claim 14, wherein the threaded rod is screwed into an opening in the ejector rod.
 16. The sampling pipette of claim 10, wherein the generally U-shaped portion comprises limbs that spread apart to accept the male portion.
 17. The sampling pipette of claim 10, wherein the generally U-shaped portion and the male portion are constructed from thermoplastic material.
 18. A detachable ejector for a liquid sample pipette, the ejector comprising a connection screw threaded into an ejector rod through a knurled wheel, wherein the ejector rod is capable of reversible assembly with a pipette body. 